This invention relates to surface breaking or scarifying tools having rotatable rollers, discs, or cutters capable of being moved over a surface to be cut or scratched. Such scarifying tools are used to perforate wallpaper.
In removing wallpaper, it is desirable to perforate or scratch the surface of the wallpaper to allow water or steam to penetrate the surface of the wallpaper to reach the glue or adhesive adhering the wallpaper to a wall. Generally, such tools have consisted of cutter wheels or spiked rollers, illustrated by the following patents:
U.K. Pat. No. 22540 of 1912, PA1 U.S. Pat. No. 3,389,466, to Parris, PA1 U.S. Pat. No. 2,435,349 to Hall, PA1 U.S. Pat. No. 3,514,814 to Norfleet, PA1 U.S. Pat. No. 4,274,202 to Petrick.
The latter patent assigned to Bonumwerke Tigges and Winckel GmbH & Co.KG, shows a pair of spiked rollers having needle points mounted on elongate rollers, with the pair of rollers inclined to one another in such a way that if the tool is moved over the surface of wallpaper, each spike performs two motions similtaneously. That is the motion resulting from rotation of the roller, and at an angle thereto, the overall motion of the device. This results in an elongated slot-like hole in the surface of the wallpaper rather than the pin pricks achieved by rotation of a single roller. The mounting of the pair of rollers, is such that if the wall surface is not particularly flat the roller on the high spots will bite more firmly into the wall and will also tend to control the movement of the device. It will wish to move in a direction normal to the axis of rotation of the roller on that side. When correcting pressure is applied to the other side, again there will be uneven depth of pricking and the movement will be in the other direction. This has not only the undesirable effect of causing the device to move in wavy lines, but also reduces the efficiency of the scratching process, because if one side "takes control", the spikes on that side will prick the wallpaper only leaving pin pricks rather than the elongate slot-like holes. In addition, the tool described in the Petrick patent has to be held at a fixed angle to the wall if all of the spikes are to contact the surface as the tool is moved along the wall. It will be readily appreciated that changing the angle of the handle relative to the wall will cause the tool to pivot about those spikes which are distant from the handle, thereby allowing the remainder of the spiked rollers to lift clear of the surface. This limits the usefulness of the tool, and with the necessity for a levelling guide makes it difficult to operate the tool in confined areas.
Another tool showing a pair of inclined rollers is U.S. Pat. No. 4,224,726 which teaches the use of pivotally mounted inclined rollers made up of star wheels to pull a carpet seam together.
U.S. Pat. No. 976,496 to Reiser describes a paper cutter using a pair of inclined meshing cutting wheels to cut a single score line to facilitate separation of the cut paper into two portions.